This invention relates to methods for the preparation of acryloxy-functional or methacryloxy-functional organosilicon compounds. More particularly, this invention relates to a very efficient method for the preparation of high-purity acryloxy-functional or methacryloxy-functional organosilicon compounds in which the generation of reaction by-products is inhibited and gelation of the reaction product does not occur.
Organosilicon compounds functionalized with the acryloxy or methacryloxy group (hereinafter abbreviated as (meth)acryloxy-functional organosilicon compounds) readily react with radically-polymerizable monomers, e.g., methyl methacrylate and styrene, and as a consequence are used as starting materials for copolymers deriving from these monomers and as modifiers for polymers obtained from these monomers.
These (meth)acryloxy-functional organosilicon compounds are prepared by addition-reacting the acrylate ester or methacrylate ester of an aliphatically unsaturated alcohol with a SiH-functional halosilane and subsequently isolating the (meth)acryloxy-functional organosilicon compound from the reaction mixture by distillative purification (Refer, for example, to Japanese Patent Application Laid Open (Kokai) Number Hei 5-301881 (301,881/1993)). However, these addition reactions are frequently accompanied by the generation of reaction by-products such as acrylic acid and methacrylic acid. Moreover, since these reaction by-products as well as the (meth)acryloxy-functional compounds are readily polymerize upon heating, these methods are also often accompanied by polymerization to high molecular weight compounds and gelation during the addition-reaction stage and during the distillation step. As a consequence, the addition reactions in these methods must be run while maintaining the reaction temperature at a level at which thermal polymerization will not occur. This type of temperature control is quite difficult, however, and the reaction products still often undergo polymerization to high molecular weights and gelation.
Japanese Patent Application Laid Open (Kokai) Number Hei 5-186478 (186,478/1993) discloses a method that uses N,N,-dialkylaminomethylenephenol as polymerization inhibitor. This inhibitor has relatively good effects in terms of inhibiting the polymerization of acrylic-functional silane and halosilane, but it is a poison of the platinum catalysts used as addition-reaction catalysts in the synthesis of these silanes by addition reaction as described above. This method thus suffers from the problem of requiring the use of large amounts of platinum catalyst to complete the reaction.
As a result of extensive investigations directed to solving the problems described above, the inventors have discovered that running the subject addition reaction in the presence of a special type of compound inhibits the generation of reaction by-products and prevents gelation during the addition reaction. Specifically, the object of the present invention is to provide a high-yield method for the synthesis of high-purity (meth)acryloxy-functional organosilicon compounds in which during the production of these compounds the generation of reaction by-products is inhibited and gelation of the reaction mixture does not occur.